1. Field of the Invention
The present invention relates to a resin composition, an insulating matrix comprising the same and a circuit board using the same. More specifically, the present invention relates to a resin composition comprising a cross-linked polymer formed by a diamine unit containing an imide group and an isocyanate unit, an insulating matrix comprising the same and a circuit board using the same.
2. Description of Related Art
Flexible circuit boards in which printing circuits are formed on flexible substrates are usually applied to various electronic devices. These flexible circuit boards comprise substrates, circuits formed on the substrates and insulating matrix for protecting the circuits.
The substrates or the insulating matrix used in these flexible circuit boards can be formed by thermal stable resin films formed by polyimide. Among the known polyimide, aryl polyimide not only has excellent thermal stability, mechanical property and flame retardancy, but also has excellent size stability. There are the reasons why the aryl polyimide can be applied to various fields. However, the polyimide sometimes is difficult to be dissolved in solvents and has higher melting point, resulting in the workability thereof reduced.
The portable phones are nowadays developed from the folding or slider phones toward the smart phones, based on advantages of large screens, thin thicknesses, delicate designs and internet functions. Applications of these advantages are even expanded, for example, portable display devices called as pads are continuously developed and upgraded inherently connected to improvement of screens and relative techniques. The demands of the display devices with more functions and small sizes cause many stricter requirements to their inside units, such as thinner thicknesses of the flexible circuit boards as well as other units. Because the flexible circuit boards are designed to deploy circuit lines, their thicknesses, flexibility and toughness are very important and have to be improved for new designs and new display devices.
Epoxy adhesive is generally used as an adhesive of the protection layer, compared with a polyimide layer and an epoxy resin layer; the protection layer adheres onto a substrate with circuits on its surface to form the flexible circuit board. However, aryl polyimide is rigid and does not have enough flexibility; and the used adhesive causes the thickness of the circuit board hard to be reduced. In some cases, thin polyimide layer is prepared to be thinner products to solve the thickness problem; but the yield of the circuit board is not good enough. In other cases, single protection layer may be formed by alloy resin of epoxy or polyimide and acrylic resin, or alloy resin of epoxy resin derived from rubber and acrylic resin; but the technique for embedding circuits into the aforesaid protection layer are not matured and the thermal stability of the obtained circuit boards is not good enough.
Therefore, it is desirable to provide a novel resin composition, and the products thereof can show excellent toughness, flexibility, film workability, thermal stability and adhesion, to solve the aforementioned problems.